Manufacture of rutile



, Patented Mar. 26, 1935 Joachim Bockstroh,

Cologne-Deutz, Friedrich Raspe, Leverkusen-I. G. Werk, and HeinrichKircher, Leverkusen-Schlebusch, Germany, as-

signors to I. G. Farbenindustrie Aktiengeaell-v schaft,Frankfort-on-the-Main, Germany No Drawing. Application April '1, 1934.Serial 7 Claims.

This invention relates to the manufacture of rutile from anatase. Itconsists in adding to the anatase a small amount of another substancewhich has the crystal structure of rutile, but be- 5 ing chemicallydifierent therefrom, and heating.

It is known that polymorphy can be observed on a number of elements andcompounds. With the difference in the crystal structure also numerousother properties related therewith, such as cleavability, optic, thermicand electric conducting power etc. may vary. In the technic it is ofimportance in such cases to manufacture from a substance only a definitemodification if this modification shows certain technically valuableproperties to a decided extent and is superior to other modifications ofthe same substance.

As is known the transformation of polymorphous substances is effectedunder certain conditions of temperature and pressure and sometimesdepends on the time during which temperature and pressure influence thecompounds.

- We have found that the transformation of anatase into rutile may beconsiderably favored by performing the transformation in' the presenceof such substances which themselves possess the crystal structure of therutile, but being chemically different therefrom, by adding thesesubstances to the anatase before or during the transformation. Theeffect of these additions is extended to the temperature atwhich-transformation may take place and also to the time, such, thateither the transformation of the anatase into rutile at the sametemperature at which otherwise the anatase istransformed, isperformed ina much shorter time or, the transformation is performed duringtheusually applied time at a lower temperature wholly or partially, butthen in a much better yield than without additions.

the advantages brought about by thetransformation, for example, those ofcolor-technical nature, by impairing other qualities.

The favorable effect of the additions can althereof; this must beconsidered a further tech- By the saving of time or the saving of energyIn Germany October 1, 1931 nical advance because undesired costs in thetechnical process are avoided.

The process may be carried out in such a manner that the additionsfavorably influencing the transformation of anatase into rutile may be 5applied before calcining in a wet or dry state to the anatase. Theadditions may also be made during the calcining process; or, calciningmay be effected in two stages, whereby the substance is added after thefirst stage. Further, the substance favorably influencing thetransformation may be formed in the mixture itself either from thesingle compounds already present in the mixture or on account of achange they undergo in the transformation process.

The invention is further illustrated by the following examples withoutbeing restricted thereto:

Example 1.--Pure dried titanic acid hydrate which according to X-rayphotography tests has proved to consist of anatase crystals isintimately mixed with 4 parts by weight of manganous sulfate or thecorresponding quantity of another manganese compoundlikewisetransforming into manganous oxide on heating, calculated upon100 25 parts by weight each of T102, and the mixture is heated to 800C., for one hour. The product thus obtained completely consists ofrutile crystals, whereas the pure titanic acid'hydrate heated withoutany additions possesses the unchanged anatase structure, and heated to900 C. for one hour is only transformed to 60% into rutile.

Example 2.--100 grams of pure T102, in the form of dried titanic acidhydrate are intimately mixed with 10.8 grams of shot (chemically pure)and calcined to 850 0.; another portion of the same mixture is heated to900 C. for one hour, and a third and fourth portion of T10: is calcinedwithout any addition at 850 C. and 900 C. respectively. The startingmaterial consists of anatase crystals. The T102 calcined'withoutadditions consists after calcining at 850C. only of anatase crystals,whereas the T102 heated at 900 C. consists of to 60% of rutile crystalsand to 40% of anatase crystals. The T102 heated with the additionishowever transformed to 20% at 850 C., and completely transformed intorutile crystals at 900 C. Instead of S110: also another tin salt, suchas tin chloride, may be applied which on. heating, is transformed intoS1102. This is a continuation in part of our co-pending applicationSerial No. 634,988, filed September 26, 1932. ready be observed whenusing small quantities We claim:--- 1 Process of preparing rutile fromanatase,

consisting in performing the transformation in the presence ofsubstances crystallizing in the rutile lattice, but being chemicallydifl'erent therefrom.

2. Process of preparing rutile from anatase, consisting in heatinganatase in admixture with a small amount of a compound crystallizing inthe rutile lattice, but being chemically different therefrom.

3. Process of preparing rutile from anatase.

which comprises heating anatase at a. temperature of about 800 to 850 C.in admixture with a small amount of a compound crystallizing in therutile lattice but being chemically difierent therefrom.

